Instagram's latest user numbers are sure to make Facebook a proud new papa.

More than 50 million people are now using the popular site and its mobile apps to upload and share photos with fellow users and friends. Instagram didn't officially release the news. The company's Press Center Web page still lists the number of registered users at 30 million.

Instead, the latest figure was obtained by tapping into the site's application programming interface, according to CNET sister site ZDNet. Instagram is apparently adding around 5 million new users per week.

CNET contacted Instagram for comment on the numbers. We'll update the story when we get more information.

The huge upswing in Instagram's audience comes hot on the heels of the company's acquisition by Facebook early last month. Facebook is shelling out $300 million in cash and 23 million shares of its own soon-to-go-public common stock, adding up to around $1 billion in total.

The iPhone version of Instagram has also proven popular. In December, Apple named it the iPhone app of 2011, dubbing it the year's "definitive photo-sharing app."

Instagram lets people tweak their photos through a series of filters designed to enhance and improve even a bad picture. Users can then upload and share their photos via their Instagram profile as well as with friends on Facebook, Twitter, or Flickr.

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Journalist, software trainer, and Web developer Lance Whitney writes columns and reviews for CNET, Computer Shopper, Microsoft TechNet, and other technology sites. His first book, "Windows 8 Five Minutes at a Time," was published by Wiley & Sons in November 2012.
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